X-Y positioners are common components of various machine systems. Such positioners are of particular utility in connection with mechanization of repetitious, usually monotonous human jobs. Such devices must be capable of moving through several degrees of freedom, i.e., in several orthogonal dimensions. Typically movement in each dimension is servo-controlled, with overall control provided by a microprocessor or a computer. In most cases, positioner movement cycles are fully programmable and can be recalled or changed at will. Ordinarily a total of up to six different degrees of freedom are provided. A number of different actuator types are known, including linear units, rotary units, combinations of these, grippers, etc. The positioner according to the invention is an X-Y positioner, having linear actuators acting in orthogonal directions.
The German journal Elektronik, Vol. 1, p. 68, 1984, describes an X-Y coordinate positioning device in which profiled rails are placed on a worktable on either side of its working surface. Motion in the X-direction is provided by a lengthwise slide which rides in a double-track guide. This slide can be moved with a handwheel. A cross-slide for motion along the Y-axis rides atop the lengthwise slide in a similar double-track guide, and can be moved with a handwheel. In place of the handwheels, DC drive or stepping motors can be used, controlled by a microprocessor, for automatic positioning in the X- and Y-axes.
This approach is workable, but suffers from the defect that the motor for the cross-slide is carried on the lengthwise slide so that it is moved when the lengthwise slide moves along the X-axis. The weight of the cross-slide motor thus contributes to the inertial load on the lengthwise slide motor, necessarily limiting its response time.